A session initiation protocol (SIP) refers to a control protocol for creating, modifying, and terminating sessions with one or more participants. SIP operates at an application layer of a communications system. Basically, SIP is a connection set-up protocol; the actual data is carried otherwise. SIP-capable user terminals are becoming more and more common. For example, Symbian OS 9.2 mobile phones supplied by several vendors are SIP compatible.
SIP applications running on a user terminal require the configuration of user terminal SIP settings. The SIP settings of the user terminal may be configured manually by the user. However, one of the problems with that approach is that configuring the SIP parameter settings manually is laborious and error-prone since a lot of information has to be entered by using the user terminal's (such as a mobile phone) limited keyboard. Also, a way of providing the settings to the user terminal is required.
WO 2006/005 790 describes a system for an automatic delivery of network configuration parameters from a network to a dynamic host configuration protocol (DHCP) server. It provides an auto-configuration of configuration parameters from network servers to hosts such as mobile terminals. According to WO 2006/005 790, if a configuration storage cannot provide the requested configuration information, the configuration storage tries to retrieve the configuration information from a network so that further requests for the missing pieces of configuration information would be successful. The DHCP server is connected to a dynamically updated configuration storage. The configuration storage stores configuration parameters such as a domain name server (DNS), e-mail, session initiation protocol (SIP), or other service dependent or independent parameters required in a terminal device to enable a specific service or application. An example of a simple format of a configuration parameter is an internet protocol (IP) address or a uniform resource locator (URL) address of a server providing a particular service. The configuration storage delivers requested configuration parameters to the DHCP server by a server's request. In the configuration storage, each service entry contains network server-specific information such as: a) a unique service identifier identifying the service in a global scope (for example, a globally unique internet assigned numbers authority (IANA) vendor ID and vendor-specific unique service ID); b) configuration data represented in a service-specific or service-independent format such that both the client and server application have the same interpretation of the data; and/or c) a time-to-live (TTL) value for the configuration data.
However, WO 2006/005 790 does not deal with actually bringing the SIP configuration to the user terminal. Although DHCP might be able to provide the required parameters, it is, however, in practise used for lower level IP configuration. SIP settings (or other settings above the IP layer) cannot be brought into current user terminals by means of DHCP. DHCP is more like a feature implemented by an operating system of the user terminal, by means of which certain network parameters are retrieved every time a data connection is formed. In addition, DHCP functions on top of an Internet protocol (IP), and, therefore, it functions only after an IP connection to a connection address has already been formed. The configuration of the SIP settings is bound to a certain connection address, such as a wireless application protocol (WAP) connection address, and DHCP cannot be used for configuring settings that are not strictly bound to the certain connection address. Examples of SIP settings that are not strictly bound to the certain connection address include a user SIP identity and a connection through which the SIP server is to be contacted. The DHCP configurable SIP enables finding, for example, a SIP service that happens to be present in a currently available network. However, the DHCP configurable SIP is not suitable for obtaining settings (such as the network connection used) for a specific SIP service necessary for a specific SIP application. For example, by means of DHCP the user terminal may find, via a wireless local area network (WLAN), a home voice over IP (VoIP) server, meaning that the application will not work since the application requires an application server which is located in the IMS system of the operator (and which is thus not present in the home VoIP network).
US 2004/0 153 548 A1 describes a configuration method for providing a configuration parameter such as a server, gateway or proxy server address(es) to a terminal device. Trigger control information defining trigger events and/or conditions is loaded to the terminal device and a discovery procedure for obtaining the configuration parameter(s) is initiated when at least one of the trigger events and/or conditions is detected. Thereby, configuration of services or server addresses can be provided to a moving mobile terminal.
US 2004/0 153 548 A1 describes a solution that is close to that of WO 06 005 790. However, US 2004/0 153 548 A1 does not relate to SIP settings. Further, US 2004/0 153 548 A1 merely concentrates on how to start the configuration. For example, it discloses that roaming or a cell change acts as a trigger for starting an undefined configuration, but it does not describe how the configuration is actually retrieved. It only lists examples such as DHCP. US 2004/0 153 548 A1, like WO 2006/005 790, merely concentrates on finding services that happen to be present in the currently available network.